1. Field of the Invention
During aircraft manufacture very large numbers of rivets are installed, precisely spaced in rows. Upon inspection of the work, it is frequently found that one rivet in the row is not headed properly, installed crookedly, or has another defect requiring its removal and replacement. This invention is part of a guide for the drill which cuts away the defective rivet or other fastener and later prepares the hole for acceptance of a replacement fastener, usually an oversize one specially made to retain all the fit and strength properties designed into the original fastener and joint The invention receives the desired size drill bushing, permits it to be located exactly, and permits of clamping to existing structure so the new rivet hole will be "perfect" and not require another rework cycle. The name industry uses for the part which holds the drill bushing in position is "drill bar".
2. Description of Prior Art
Depending on the location and surroundings of the defective fastener to be replaced, a variety of approaches is called for. Typically existing drill bars are held in place from one side only, the bushing holder being on one end of the bar. Sometimes the bar is held down by removing nearby rivets, the holes of which may then be used for clamping bolts. Existing drill bars usually have a wide (say 3/8 inch) slot through which a 1/4 inch diameter holddown bolt passes. There is obviously no possibility of drilling the frame or panel to create a mounting hole for the repair tool, but C clamps are also often usable to avoid removing sound rivets, and the risk associated with doing that. It should also be mentioned that, since each rework is unique, grinding away part of existing drill bars to fit the circumstances is very common.
My invention basically provides an adjustable-angle dogleg in the length of the drill bar, resulting in two embodiments, permitting either two-sided holddown of the bar or allowing holddown to occur outside the line of fasteners and avoiding removal of good fasteners solely to anchor the drill bar. Both embodiments allow easier clamping to the various contours likely to be present in fastener-lines in aircraft. Also using narrow slots as holddown means restricts sliding under the anchor bolts to one direction which expedites installation.